Study On The Collision Rule And Erosion Characteristic Of Solid-liquid Two-phase Flow With Large Particle Diameter

At present,The mainly methods to study the solid-liquid two-phase flow are experiment and numerical simulation,but the research on large particles solid-liquid two-phase flow is insufficient,There is no suitable collision model for large particle solid-liquid two-phase flow numerical simulation.Therefore,there is large deviation in numerical simulation of large particle solid-liquid two-phase flow.In this paper,The experimental research of large particle solid-liquid two phase flow was carried out firstly.The collision model for large particle solid-liquid two-phase flow was concluded according to the experimental research which can modify the particle-wall collision.Secondly,the numerical simulation of solid-liquid two flow with DPM model in square elbow was carried out.The influences of various factors on the erosion rule of the elbow was analyzed,and the elbow structure was improved to reduce erosion rate and prolong the service life of the elbow.The following is the main research content:(1)In order to study the rule of particle-wall collision rule with different diameters and wall material in air and water,the particle-wall collision experiment device was built.It was found that the restitution coefficient of particle-wall collision is independent with the particle size(3mm-7mm),and it is related to the medium,the impact angle,the wall material and the impact velocity.In the end,the collision model for large particles is abstained.(2)Through visualization experiment of solid-liquid two-phase flow bend,obtaining particle trajectory in bend,and compared with the particle trajectory which was obtained by numerical simulation with different collision model.It confirmed that the commonly used two-phase flow collision model is not suitable for the numerical simulation of solid-liquid two-phase flow with large particle diameter,and the collision model which obtained by the collision experiment has high accuracy for solid-liquid two-phase flow with large particle diameter.(3)Using SolidWorks to build three dimensional model of the inlet side of the 80 mm square elbow,Then using workbench for meshing.Finally,using CFD software fluent with the collision model obtained by the particle-wall collision experiment to calculate the square elbow.The effects of particle diameter,flow rate,particle mass flow rate,gravity direction,particledensity and particle Stokes number on the erosion rules of the elbow were analyzed,a series of rules can be taken to prevent and predict the erosion failure.(4)The elbow structure was improved,by means of adding the side baffle plates on both sides of the elbow section and adding the transverse baffle on the outer side wall of the elbow section,The influence of the Secondary flow vortex on uneven erosion distribution was solved effectively,The maximum erosion rate and the average erosion rate of the elbow was reduced.However,the transverse baffle will cause some pressure loss,and the greater the speed,the greater the pressure loss.